It is known to equip air-conditioning installations of motor vehicles with filters, particularly with activated carbon filters. The filters clean the air being supplied to the vehicle interior of strongly smelling and/or toxic components. However, the absorbing power of activated carbon drops off over time, so that the activated carbon has to be cleaned or exchanged. Because the exchanging of the activated carbon filter, particularly with motor vehicles, is associated with high expenditure and high cost, ways for effective regeneration of the activated carbon are sought.
It is known, for example, to install a heating device, on the air intake side, in series with the activated carbon filter. The heating device heats up the airflow through the filter and hence the filter itself, and which leads to a desorption of the residues in the filter. The contaminated airflow can then be led away to the environment. The disadvantage of this series-connected heating it is that the cleaning takes place in an adiabatic process. Because the airflow is cooled down on passing through the filter by vaporising of the contamination, the desorption process is longer and hence the external energy consumption for the blower is comparatively high.
On the other hand, filters with activated carbon filling are known, in which rod-shaped electrical heating elements are inserted directly into the mass of activated carbon, so that they heat the activated carbon itself. With the heating rods inserted vertically, it is not possible to heat the entire filter uniformly.
It is a further disadvantage that the heat conduction into the activated carbon surrounding the heating rod is so slight that the heating rods have to be heated to a particularly high temperature in order to produce a sufficient temperature for the cleaning. The heating rods, heated to high temperature, therefore present a great danger as regards ignition of the carbon in contact with the heating rods. A cleaning installation of this type does not meet modern-day safety standards, so that it is impossible to install it in motor vehicles.